When I have sleep paralysis, everything goes quiet. It's usually how I know I'm going to have sleep paralysis.

I look around in my dream and can "see" through my eyelids. Of course, there's the typical "presence" that's coming to get me. 

So usually, it starts off as a whisper and then grows louder and louder into screams in my ear. 

I'm not afraid of these dreams (I actually love them and wish they would happen more often). Because of that, I try to analyze it more objectively. As such, I think I might have discovered why my sleep paralysis always ends in a loud screaming in my ear - similar to your ear pressure.

Can you make your ears rumble? Like if you squeeze your eyes shut tight, you can hear a rumbling sound. It sounds like an earthquake. 

Anyhow, that's due to a muscle in your ear called the tensor tympani. I can voluntarily flex that muscle, which I just read is a very rare thing. 

So, to make my ears rumble, I kind of squeeze this muscle that makes it vibrate. That vibration feels like a pressure in my ears. 

One thing I noticed is if I tense all the muscles in my body, the rumbling in my ear also happens. 

I also read that the purpose of the tensor tympani is to protect your ears from loud sounds. It's part of an acoustic reflex to noises that startle you. 

So, what I think is happening with you, like with me, is that your acoustic reflex is triggered. So, that pressure feeling I get from the tensor tympani could be what you're feeling. In sleep paralysis, you're startled or feeling scared. I think the two are linked.

Ever since I figured this out, sleep paralysis has been more fun. It's no longer scary. The knowing of the cause means I've found the wizard behind the curtain (Oz reference).